Inconel 725 is a precipitation-hardenable nickel-chromium alloy with additions of niobium, titanium, and molybdenum. It was specifically developed to provide high strength and exceptional corrosion resistance in severe environments, particularly those containing .
The key to its performance is a two-step thermal treatment process (aging) that precipitates gamma prime and gamma double prime phases throughout the matrix, significantly increasing its strength. This makes Inconel 725 pipe an excellent choice for demanding applications in the oil and gas, marine, and chemical processing industries.
environments (high H₂S and chloride concentrations).
chloride-induced stress corrosion cracking (SCC).
Good resistance to pitting, crevice corrosion, and general corrosion.
Achieves very high yield and tensile strength through aging treatment, comparable to or exceeding high-strength OCTG grades.
It can be hot- or cold-worked using standard methods and can be welded using matching filler metals (e.g., INCONEL Welding Electrode 725).
The typical chemical composition of Inconel 725 is as follows:
| Min. | 55 | 19 | - | 7 | 2.75 | 1.0 | - | - | - | - | - | - |
| Max. | 59 | 22.5 | 15 | 9.5 | 4.0 | 1.7 | 0.35 | 0.03 | 0.35 | 0.20 | 0.003 | 0.2 |
The properties of Inconel 725 pipe vary depending on its size, manufacturing process, and heat treatment condition. The following table provides typical properties for aged (precipitation-hardened) material.
| Yield Strength (0.2% Offset) | Elongation (in 50mm) | Kekerasan (Rockwell C) | ||
|---|---|---|---|---|
| >= 1100 MPa (160 ksi) | >= 795 MPa (115 ksi) | >= 20% | 28 - 40 HRC |
| 8.22 g/cm³ (0.297 lb/in³) | |
| 1270 - 1340 ℃ (2320 - 2450 ℃F) | |
| Thermal Expansion Coefficient (20-100℃) | 12.8 μm/m·℃ (7.1 μin/in·℃F) |
| 11.5 W/m·K (80 BTU·in/hr·ft²·℃F) | |
| 206 GPa (30 x 10⁶ psi) |
To achieve the optimal combination of strength and corrosion resistance, Inconel 725 is subjected to a two-step aging process
Typically performed at 1750-1850℃F (955-1010℃), followed by rapid quenching.
1400℃F (760℃) for 8 hours, furnace cool to
1300℃F (705℃) for 8 hours, air cool.
Inconel 725 pipe and tubing are produced to meet various industry standards, including:
ASTM B829 (Standard Specification for Seamless Nickel and Nickel Alloy Condenser and Heat-Exchanger Tubes)
ASTM B805 (Standard Specification for Precipitation Hardening Nickel Alloy Bars, Forgings, and Forging Stock for High-Temperature Service)
NACE MR0175 / ISO 15156
API 6ACRA (Standard for Age-Hardened Nickel-Based Alloys for Oil and Gas Drilling and Production Equipment)
Inconel 725 pipe is primarily used in extremely aggressive environments where standard stainless steels and lower-grade nickel alloys fail. Key applications include:
High-strength production tubing and casing for deep, sour wells.
Downhole equipment (hangers, subs, valves).
High-strength fasteners, bolts, and components for subsea systems.
Components in seawater cooling systems.
Piping and reactors handling hot, concentrated chlorides and other aggressive media.
Inconel 725 is a trademark of Special Metals Corporation. The information provided here is typical and for reference purposes only. For critical applications, always consult the official data sheets from the material manufacturer and the specific pipe supplier.
